Picked up a spare copy of this album today and gave it a spin, haven't heard it for a few years. I'm pretty sure most of the vocal tracks are Chris Bartley, but for me the best track "What Kind Of Man" almost certainly isn't.
I'm pretty sure it isn't Van McCoy singing as his style is very MOR on most of his records and the only soulful record, "Let Me Down Easy", I have by him has no vocal similarity. So after a bit of investigating I'm leaning towards it being Oscar Weathers who cut a few tracks on Top & Bottom with Van McCoy.